When a desktop has less throughput than a laptop

I have a desktop PC running XP Home and a laptop running Vista. The desktop is connected to a router via a cable and the laptop is wireless. The broadband speed on my laptop can run up to 6Mb but my desktop varies from 0.3 to 1.8Mb. Why does my desktop run so much slower than my laptop?
-- Geraint L. Jones

I would expect the broadband speed to be the same for both connections, so let's see if we can figure out why it isn't. The first thing I would do is go to Web site for the vendor of your wireless router and get the latest firmware. Although I don't think this is the issue, using the latest firmware tends to reduce the number of variables we need to look at.

That out of the way, look at the path the cable takes from your laptop to the router. If it is mixed in with power cables, runs near or over a fluorescent light fixture or something with a motor in it, that could be inducing electrical noise into the network cable, which would slow the maximum speed it can support. Even if the cable is in the clear, there could still be damage to the wiring that you can't see without getting inside the insulation, so try a different cable and see if that helps. Another thing to try is a different port on the router

The next thing to look at is the network card itself. I would try hard coding the network card for 100-Megabit speed and full duplex. Auto speed/duplex negotiating can sometimes cause problems. Normally I would expect this to be just a duplex setting problem as a speed setting mismatch should result in no communications occuring at all between the computer and the router.

If the problem persists, try a USB network card and disable the onboard card in your computer. If this resolves the problem, that would indicate that the network card in the computer is having a problem. If so, try locating and installed updated network card drivers to see if this helps with the onboard network card. If this doesn't fix the problem and the USB card does get better speed, you may need to look at replacing the non-USB network card - unless it is integrated into the motherboard, in which case you might just want to stick with the USB card (and if so, you will need to make sure that you disable the first network card permanently).

Source: Network World